1. FIELD OF THE INVENTION
The present invention relates to a silver halide photographic emulsion spectrally sensitized with a novel merocyanine dye, and, more particularly, to a silver halide photographic emulsion having high blue- and green-sensitivities.
2. DESCRIPTION OF THE PRIOR ART
Many kinds of cyanine and merocyanine dyes have been used for the spectral sensitization of silver halide photographic emulsions. Of such dyes, merocyanine dyes are disclosed in U.S. Pat. Nos. 2,493,747, 2,493,748, 2,497,876, 2,519,001, 3,384,486, 3,480,439, 3,625,698, 3,765,901, etc. Though many kinds of merocyanine dyes have been used as above, the practical spectral sensitization powers thereof are not sufficient. Some merocyanine dyes can provide a good spectral sensitizing function but cannot be practically used because they often cause fog and decrease the sensitivity of light-sensitive materials during storage thereof. Further, such dyes often remain in silver halide emulsion layers after development and stain the photographic images therein. It has long been desired in the art to overcome these technical problems of the merocyanine dyes.